System of controlling traffic signals

ABSTRACT

A coordinated traffic signalling control system comprises a plurality of local controllers having no interconnecting cables. Each controller includes a radio receiver tuned to receive a standard frequency and time transmission, broadcast by a preexisting standard signal services station, such as WWV; and a time signal discriminator coupled to the receiver generates time signals from the received radio signals. A programmer circuit, responsive to the generated time signals, in turn generates traffic pattern instruction signals. Circuits responsive to the generated timing signals and to the generated pattern instruction signals, automatically control the offset and split selection for that controller.

United States Patent [54] SYSTEM OF CONTROLLING TRAFFIC SIGNALS 8 Claims, 1 Drawing Fig.

[52] US. Cl 340/40 [51] Int. Cl G08g 1/07 [50] Field of Search 340/40 Primary Examiner-William C. Cooper Attorney-Moore and Hall ABSTRACT: A coordinated traffic signalling control system comprises a plurality of local controllers having no interconnecting cables. Each controller includes a radio receiver tuned to receive a standard frequency and time transmission, broadcast by a preexisting standard signal services station, such as WWV; and a time signal discriminator coupled to the receiver generates time signals from the received radiosignals. A programmer circuit, responsive to the generated time signals, in turn generates traffic pattern instruction signals. Circuits responsive to the generated timing signals and to the generated pattern instruction signals, automatically control the offset and split selection for that controller.

SYSTEM OF CONTROLLING TRAFFIC SIGNALS The present invention relates to a system of controlling traffic signals, more particularly to a method for regulating signal installations of a multistage coordinated control system to synchronize with one another, and to an apparatus for performing the method. The invention to be described constitutes an improvement on the invention described in our prior British Pat. No. 1,086,664, imued Oct. 1 l, 1967, for An Offset Control System for Trafiic Signal.

In order to control a plurality of local controllers of traffic signals, coordinated control has been elTected heretofore by interconnecting the local controllers with one another through cables, and by delivering control signals through such cables from a master controller. This conventional approach, however, has been expensive in the cost of cables and construction resulting from the fact that the local controllers must be connected with one another by means of cables. Moreover, since thecables employed are usually installed at relatively high locations maintenance and checking of the cables have also been inconvenient.

Accordingly, it is a main object of the present invention to provide a novel method of adjusting coordinated traffic signal installations, to synchronize with one another, by the reception and utilization of standard signals transmitted for general reception by standard signal radio stations, such as station WWV in Beltsville, Md., and/or station WWVH, Maui, Hawaii.

Another object of the present invention is to provide an apparatus for carrying out the above-described method.

Other objects, features and advantages of the present invention will be apparent from the following detailed description taken in conjunction with the accompanying drawing in which the only drawing shows a schematic block diagram illustrating one embodiment of an apparatus for carrying out the method of adjusting traffic signal controllers to synchronize with one another in accordance with the present invention.

Now, reference will be made to one embodiment of the present invention shown in the drawing.

First, in a system of controlling coordinated traffic signals provided in a local controller, standard-signal receiver 1 is provided to receive a standard frequency and time transmission from a standard-signal services radio station, such as station WWV. The received radio signal is delivered into a-time discriminator circuit 2. The circuit 2 discriminates the information in the received signal, i.e. the width of a clock pulse, the interruption of the radio wave, and the Morse code of time, and produces a time signal which is delivered to a programmer3 and a coder 8. The programmer 3 has a timing portion and a pattern establishing portion, and is adapted to deliver a predetermined signal to a circuit 4 for establishing a signal cycle length and one of split offset determining circuits 14-1, 14-2, l4-n, respectively, when the output of the timing portion is coincident with a predetermined pattern of the pattern establishing portion. The split and offset circuits, and their operation, are described in British Pat. No. 1,086,664. The pattern establishing portion of programmer 3 replaces the master controller of said British patent, and is responsive to the time signal from circuit 2 to generate a pattern set, or traffic pattern instruction signals, establishing the appropriate values of the cycle, offset, and split for that controller. The signal cycle length establishing circuit 4 in which there is set a period corresponding to a selected pattern instruction of the pattern establishing portion of the programmer 3 determines the scale of a first variable scale counter 6 by receiving a set signal for establishing a corresponding signal cycle length signal from the programmer. The first variable scale counter 6 receives an input of a pulse ofa predetermined period which is produced by an oscillator or from the frequency of the commercial power, and converts the received pulse into asignal having a cycle length in accordance witha signal entered from the signal cycle length establishing circuit 4, the signal thus obtained being transmitted to a second variable scale counter 7 and a sync counter 9. The sync counter 9 counts the cyclic signal to thereby develop a sync pulse every cycle, and the sync signal is then transmitted to an offset adjusting circuit 10. The sync counter 9 is adapted to periodically be reset by the coder 8 which gates the time signal delivered from the time discriminator circuit 2.

The other local controllers are also adapted to be reset at the same time in a similar manner, and thus, all the local controllers develop their sync signals simultaneously.

The second variable scale counter 7 operates as a scale of m counter to count m digits when it receives a normal instruction signal from the offset adjusting circuit 10. The counter 7 i also operates as a scale of (ma) counter to count m-a digits when it receives an advance" instruction signal and operates as a scale of (m+a) counter to count m+a digit upon receiving a "delay" instruction signal. Now, assume that a normal" instruction signal is entered into the second variable scale counter 7, then the counter 7 makes an m digit count and develops one output pulse after receiving m input pulses. This output pulse is delivered to the first counter 11 whereby the counter effects a decimal digit count. Further, the output signal of the counter 11 is entered into a second counter 12, in which a decimal count is made. In other words, by utilizing both counters 11 and 12, digit counts or a 100 percent indication, can be achieved. The first and second counters 11 and 12 are connected to areference split circuit 13 (which is usually set at 0 percent) and n numbers of the split-offset determinating circuits 144, 14-2, 14-n. Each of these split-offset determining circuits provides a predetermined split and ofiset, whereby a pulse is developed at one set point of the split-offset determining circuit selected by the programmer 3. The reference split circuit 13 establishes a signal for beginning the traffic movement phase along an arterial road, and a signal for terminating said traffic movement phase is established by a pulse developing at a split set point of the split-offset deter mining circuit 14. The split pulse delivered from the circuit 13 and the offset determining circuit 14, therefore, is sent to the next circuit to be a signal for switching optical units. Furthermore, the offset pulse generated by the split offset determining circuit 14 is also delivered to the offset adjusting circuit 10 through an OR circuit 15.

Thus, if the offset pulse transmitted to the offset adjusting circuit 10 is in coincidence with the output or the sync signal of the sync counter 9, the offset adjusting circuit 10 becomes nonnal," so that the second variable scale counter 7 makes m digit counts as described above. On the other hand, if the offset pulse is delayed by above 50 percent of one cycle with respect to the sync pulse, the offset adjusting circuit 10 is in its delay condition, so that the second variable scale counter 7 counts (m+a) digits. When the delay of the offset pulse as described above is within 50 percent, the offset adjusting circuit 10 goes into its advance" condition, so that the counter 7 counts (ma) digits. Furthermore, if there is a slight advance of the offset pulse the counter 7 is made to stop by a stop signal. ln such a manner, the offset pulse is made to gradually approach the sync pulse by a 50 percent shifting even when there is maximum delay of the offset pulse. As a result, within several cycles the offset pulse is in coincidence with the sync signal. At that time, in order to prevent the occurrence of hunting the second variable scale counter 7 is stopped by means of a stop signal when the offset pulse is within a predetermined time of period, 100 a/m percent of one cycle, for example, 10 to 12.5 percent, before a sync pulse comes in while the counter 7 begins to operate again when receiving a sync pulse.

As described above, the present invention is such that an offset is adjusted by the use of a radio wave of a standard signal as each local controller is corrected to synchronize, thus each local controller being synchronized. Therefore, the present invention needs no cables such as are used in conventional coordinated control systems, and achieves significant advantages in that the installation of traffic controllers is simplified, and less expensive, and the maintenance and extension of the controllers are facilitated.

What we claim is:

l. A coordinated traffic signalling control system comprising a plurality of local controllers, each of said controllers including an offset circuit and a split circuit, radio receiver means at each controller tuned to receive the standard frequency and time signals broadcast for general reception by a preexisting standard signal radio station, a time discriminator circuit coupled to said receiver for generating timing signals from the broadcast signals received by said receiver, programmer means responsive to said generated timing signals for generating traffic pattern instruction signals, and control means responsive to said generated timing signals and to said generated trafiic pattern instruction signals for controlling the operation of said offset and split circuits.

2. The combination of claim 1 wherein said control means includes an offset adjusting circuit, and counter means connected to said split circuit, to said offset circuit, and to said offset adjusting means.

3. The combination of claim 2 including means coupling said traffic pattern instruction signals to a portion of said counter means, whereby said counter means generates a sync pulse and a cyclic pulse in accordance with said instruction signals.

4. The combination of claim 1 wherein said control means includes counter means responsive to said traffic pattern instruction signals for generating a sync pulse and a cyclic pulse in accordance with said instruction signals, offset pulse and split pulse generating circuits including further counter means controlled by said cyclic pulse, an offset adjusting circuit, means coupling said sync pulse to said offset adjusting circuit, said offset adjusting circuit being operative to compare said sync pulse with the pulses generated by said offset pulse and split pulse generating circuits for selectively generating a correcting signal, and means coupling said correcting signal to said further counter means to control the outputs of said offset pulse and split pulse generating circuits.

5. The combination of claim 1 wherein said control means includes means responsive to said traffic pattern instruction signals for generating a sync pulse and a cyclic pulse, said offset circuit including means responsive to said cyclic pulse for generating an offset pulse, and means for comparing said generated offset pulse and said sync pulse, said comparing means being operative to selectively generate a correcting signal for controlling the operation of said offset circuit.

6. The combination of claim 1 wherein said control means includes means responsive to said traffic pattern instruction signals for generating a sync pulse and a cyclic pulse, said split circuit including means responsive to said cyclic pulse for generating a split pulse, and means for comparing said generated split pulse and said sync pulse, said comparing means being operative to selectively generate a correcting signal for controlling the operation of said split circuit.

7. A coordinated traffic signalling control system having a plurality of local controllers, each controller including radio receiver means for receiving a radio wave signal from an external radio station thereby to control traffic signals synchronously with other controllers, said receiver means being tuned to a transmitting station broadcasting standard frequency and time signal emissions in the service area in which the traffic signalling control system is located, each local controller comprising time signal discriminator means for developing a series of time signals from the standard frequency and time signal received by said receiver means, a traffic control pattern selector responsive to said developed time signals and operative to generate a selected pattern of instruction signals, means responsive to said instruction signals for generating a sync pulse and a cyclic pulse in accordance with selected instruction signals, an offset and split circuit coupled to said pattern selector for control thereby, counter means responsive to said cyclic signal for further controlling said offset and split circuit, whereby said offset and s lit circult generates an output corresponding to said selecte traffic control pattern, and an offset control circuit connected to compare said sync pulse with the output of said offset and split circuit, said offset control circuit being operative in response to said comparison to generate a correcting signal to vary the output of said offset and split circuit.

8. The system of claim 7 wherein said means for generating said sync pulse and said cyclic pulse includes further counter means. 

1. A coordinated traffic signalling control system comprising a plurality of local controllers, each of said controllers including an offset circuit and a split circuit, radio receiver means at each controller tuned to receive the standard frequency and time signals broadcast for general reception by a preexisting standard signal radio station, a time discriminator circuit coupled to said receiver for generating timing signals from the broadcast signals received by said receiver, programmer means responsive to said generated timing signals for generating traffic pattern instruction signals, and control means responsive to said generated timing signals and to said generated traffic pattern instruction signals for controlling the operation of said offset and split circuits.
 2. The combination of claim 1 wherein said control means includes an offset adjusting circuit, and counter means connected to said split circuit, to said offset circuit, and to said offset adjusting means.
 3. The combination of claim 2 including means coupling said traffic pattern instruction signals to a portion of said counter means, whereby said counter means generates a sync pulse and a cyclic pulse in accordance with said instruction signals.
 4. The combination of claim 1 wherein said control means includes counter means responsive to said traffic pattern instruction signals for generating a sync pulse and a cyclic pulse in accordance with said instruction signals, offset pulse and split pulse generating circuits including further counter means controlled by said cyclic pulse, an offset adjusting circuit, means coupling said sync pulse to said offset adjusting circuit, said offset adjusting circuit being operative to compare said sync pulse with the pulses generated by said offset pulse and split pulse generating circuits for selectively generating a correcting signal, and means coupling said correcting signal to said further counter means to control the outputs of said offset pulse and split pulse generating circuits.
 5. The combination of claim 1 wherein said control means includes means responsive to said traffic pattern instruction signals for generating a sync pulse and a cyclic pulse, said offset circuit including means responsive to said cyclic pulse for generating an offset pulse, and means for comparing said generated offset pulse and said sync pulse, said comparing means being operative to selectively generate a correcting signal for controlling the operation of said offset circuit.
 6. The combination of claim 1 wherein said control means includes means responsive to said traffic pattern instruction signals for generating a sync pulse and a cyclic pulse, said split circuit including means responsive to said cyclic pulse for generating a split pulse, and means for comparing said generated split pulse and said sync pulse, said comparing means being operative to selectively generate a correcting signal for controlling the operation of said split circuit.
 7. A coordinated traffic signalling control system having a plurality of local controllers, each controller including radio receiver means for receiving a radio wave signal from an external radio station thereby to control traffic signals synchronously with other controllers, said receiver means being tuned to a transmitting station broadcasting standard frequency and time signal emissions in the service area in which the traffic signalling control system is located, each local controller comprising time signal discriminator means for developing a series of time signals from the standard frequency and time signal received by said receiver means, a traffic control pattern selector responsive to said developed time signals and operative to generate a selected pattern of instruction signals, means responsive to said instruction signals for generating a sync pulse and a cyclic pulse in accordance with selected instruction signals, an offset and split circuit coupled to said pattern selector for control thereby, counter means responsive to said cyclic signal for further controlling said offset and split circuit, whereby said offset and split circuit generates an output corresponding to said selected traffic control pattern, and an offset control circuit connected to compare said sync pulse with the output of said offset and split circuit, said offset control circuit being operative in response to said comparison to generate a correcting signal to vary the output of said offset and split circuit.
 8. The system of claim 7 wherein said means for generating said sync pulse and said cyclic pulse includes further counter means. 